As an operation input apparatus for remotely operating a slave arm having a joint, in the related art there is a known medical system provided with a master arm having a joint structure similar to the joint structure of the slave arm is known (e.g., refer to Patent Literatures PTL 1 and PTL 2 below). In such a system, because the slave arm can be made to reproduce a motion corresponding to the motion of the master arm, an operator can intuitively operate the slave arm while directly recognizing the shape and motion of the slave arm from the shape and motion of the master arm.
During an actual surgical operation, it is necessary to move the slave arm not only minutely but also by a comparatively great amount when, for example, pulling an affected area or tying a knot after hooking a needle. In this case, because an operator needs to pay attention to the positional relationship between the slave arm and peripheral tissues inside the body of the patient, he or she wishes to accurately perceive the shape and orientation of the entire slave arm, including the joint part. Meanwhile, when performing intricate treatment of, for example, the affected area, it is necessary to accurately move a distal end of the slave arm provided with a distal treatment part. In this case, the operator wishes to focus attention only on the operation of the distal end of the slave arm without paying attention to the overall shape or orientation of the slave arm.
On the other hand, scale conversion techniques between a master and a slave that differ in structure are generally well known (e.g., refer to Patent Literature PTL 3). In contrast, for a master and a slave that are similar in structure, such as for the system of Patent Literatures PTL 1 and PTL 2, the ratio of the amount of motion of the slave arm to the amount of operation of the master arm (motion scale ratio) is uniquely determined according to the structure ratio between the master arm and the slave arm, and it may not be possible to change the operating condition of the slave arm, depending on the circumstances.